1. Field of Invention
The present invention relates to a golf club, particularly to the structure of its head.
2. Prior Art
Conventionally, as was disclosed in Japanese Patent Un-Examined Publication No. 9-38248, it is widely recognized to provide a golf club whose head is metallic and formed hollow. Such conventional head was constructed by for example joining a plurality of metallic shells together, said shells being formed by forging or the like.
In the past, such kind of conventional golf club had its upper surface or crown formed smooth, without any irregularities both on its outside surface and on its inside surface, though it was slightly curved. However, with such smooth crown, a relatively weak strength is resulted. A crown of a golf club does not require so great a strength as a ball-striking face thereof, but must be strong to a certain extent to withstand impacts developed in striking balls. Therefore, the material of the crown was formed thick to a certain extent in the past, which however would make it difficult to enlarge a head without increasing the weight of the head. With a large-sized head, even a beginner player can strike balls without failures, which advantage comes to nothing if the weight of the head is increased. Further, as a certain proportion of the whole weight has to be distributed to the crown, a degree of freedom in weight distribution relative to the whole head would be decreased. For example, whilst the center of gravity should be low in order to elongate the travelling distance of balls, the relatively heavy weight of the crown inevitably leads to the high center of gravity.